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Advice on fuel/air ect

just got my 3.2 v6 inlet runners back from being smoothed and polished and my question is this......they are going on to my 2.5 v6,will my thottlebody be able to throw enough fuel in without it being to lean?,or a friend has said that a adjustable fuel pressure regulator may be needed?,if so?,any recommendations?.
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Don't worry, those throttles are both the same, be happy.
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The fueling isn't down to your throttle body, it's down to the timing and capacity of the injectors.

I've run a 3.2 v6 in both cf2 and cf3 cars which should have a 2.5 v6 with no changes to the engine management and had no issues.

i.e. the ecu has plenty of capacity to cope with the changes you've made and then some.
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I thought they ran lean if you put the 3.0/3.2 runners on a 2.5V6 engine with the std ECU map?
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Why would anything run unexpectedly lean/rich if the injected fuel volume is calculated proportional to the real air mass measured by MAF?


Assuming the injector size matches the ECU injector size value. If those doesn't match, ECU compensates the fuel volume according to the feedback from lambda in closed loop mode. In open loop it would run lean/rich (depends if injector is smaller than ECU thinks or not).

Last edited by yan.ko; 15-02-14 at 14:20.
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Quote:
Originally Posted by yan.ko View Post
Why would anything run unexpectedly lean/rich if the injected fuel volume is calculated proportional to the real air mass measured by MAF?


Assuming the injector size matches the ECU injector size value. If those doesn't match, ECU compensates the fuel volume according to the feedback from lambda in closed loop mode. In open loop it would run lean/rich (depends if injector is smaller than ECU thinks or not).
but will the 2.5 fuel injectors [yellow ones] compensate for the more fuel need it ?
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I think it was when under full load that the larger runners on a 2.5V6 with the std 2.5V6 map run lean.
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Quote:
Originally Posted by David C View Post
I think it was when under full load that the larger runners on a 2.5V6 with the std 2.5V6 map run lean.
It would be so in MAP based calculated injection, if the larger runner affected the volumetric efficiency. The VE(%) map would need to be corrected then.

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but will the 2.5 fuel injectors [yellow ones] compensate for the more fuel need it ?
Injector will not compensate for anything, it's just "a well throughput measured pipe with cap". It's ECU who tells the injector when to open and when to close. And then it's just a matter of "pipe" throughput, timeframe for fuel delivery and amount of fuel you want to deliver.

Last edited by yan.ko; 15-02-14 at 15:01.
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Originally Posted by yan.ko View Post
It would be so in MAP based alculated injection, if the larger runner affected the volumetric efficiency. The VE(%) map would need to be corrected then.
so it will need a remap then
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Originally Posted by danielmk323 View Post
so it will need a remap then
If it affects the volumetric efficiency and only if the calculation is based on pressure sensing (MAP) rather than airmass (MAF).
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If it affects the volumetric efficiency and only if the calculation is based on pressure sensing (MAP) rather than airmass (MAF).
It doesn't have a MAP sensor.
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So it's easy then
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Quote:
Originally Posted by danielmk323 View Post
but will the 2.5 fuel injectors [yellow ones] compensate for the more fuel need it ?
Quote:
Originally Posted by David C View Post
I think it was when under full load that the larger runners on a 2.5V6 with the std 2.5V6 map run lean.
Perhaps, as you know, the mixture's based on lamda and air flow meter readings but I think the ecu doesn't pay much attention to lambdas at high load/revs and therefore is reliant on the MAF and fuel trims.

Gus did mention that the 2.5's run relatively lean at high revs too. So maybe there is some benefit to be had from a remap but that could be down to it running lean rather than there being an inherant problem with fitting the larger intake runners.

TBH, as the 2.5 is overvalved to begin with all I can see the bigger runners doing is further reducing the torque availible at low revs...

In addition, I did get a decent power figure from the 3.0 I was running on 2.5 injectors (247bhp IIRC) and cf3 managment which suggests to me that the ecu can cope and uses the MAF figures to good effect.
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ECUs (like ME2.1 in 2.5/3.0V6) calculate injection timeframe to get the stoich mixture according to the MAF sensed airmass. Then there is multiplicative factor (like shown below) applied to it according to the engine load and rpm.

Signal from lambda is feedback used to finetune the mixture in closed loop mode (partial throttle - probably just because the first (narrowband) lambda sensors can't sense the rich mixture exactly)

map.jpg

Last edited by yan.ko; 18-02-14 at 21:01.
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